Pulse generating circuit



March-31, 1953 G. P. WACHTELL PULSE GENERATING CIRCUIT Filed Oct. 19,1945 INPUT ATTORNEY.

Patented Mar. 31, 1953 NT OFFICE PULSE GENERATING CIRCUIT George P.Wachtell, Cambridge, Mass., assignor, by mesne assignments, to theUnited States of America as represented by the Secretary of WarApplication October 19, 1945, Serial N5. 623,392

This invention relates generally to electrical circuits, and moreparticularly to pulse generating circuits.

In one type of pulse generating circuit the control grid and anode of avacuum tube are coupled together by a transformer in a regenerativemanner. The control grid employs grid leak biasing and the cathode isnormally grounded. Such a circuit is known to those skilled.

in the art as a blocking oscillator. Blocking oscillators as well asother pulse generating circuits sometimes do not produce a pulse whoseleading edge is sufiiciently steep for accu-:

rate ranging, and the like when used with radio objects locatingdevices. Also some pulse generating circuits do not produce pulses ofsuf-" ficient amplitude. .-It is an object of this invention to providea circuit which when initiated by a signal will Other objects, features,and advantages of this invention will suggest themselves to thoseskilled in the art and will become apparent from the fol-, lowingdescription of the invention taken in con-. nection with theaccompanying drawing in which the sole figure is a circuit diagram ofone embodiment of the invention.

Referring now to the drawing, the circuit com- I prises a vacuum tubeII, pulse transformer I2, and a voltage divider network. Said voltagedievider network'is connected between a source of positive potential andground and consists of re-f The junction of resistors I3 and I4 isidentified as I5. Anode sistor I3 and resistor I4 in series.

I6 of tube II is connected to the source of positive potential throughthe primary winding I! of the pulse transformer I2. secondary winding I8of pulse transformer I2 is connected to control grid I9 of vacuum tubeII."

The other terminal of the secondary winding I8 is coupled tocathode 20of vacuum tube II through capacitor 2| and is returned to ground,

through resistor 22. The cathode 20 is connected to the. point I5.

In operation, the cathode 20 is at a positive potential due to thevoltage divider action of resistors I3 and I4, the grid is normally atground potential, and the vacuum tube II is normally maintained in anonconducting state. Negative One terminal of the 3 Claims. (Cl. 250-27)saturation region.

trigger pulses are applied to the anode I B of vacuum tube II throughcoupling capacitor 23. It will be seen from the polarity markings of thepulse transformer I2 that a'negative input trigger will cause thevoltage between cathode 20 and control grid I9 to decrease. This willcause the vacuum tube II to conduct. Conduction will cause the anode todrop in potential, thereby causing the grid to rise in potential. Thisregenerative action continues until the vacuum tube II is operatinginthe non-linear Conduction will then start decreasing, causing theanode It to rise in potential, thereby causing the control grid I9 todrop in potential. When the voltage between cathode 20 and control gridI9 reaches cut-01f potential, conduction will stop. There will be apositive overshoot at the anode I6 due to self inductance of the primarywinding. This will cause a negative overshoot in the cathode controlgrid voltage. Meanwhile, capacitor 2| has become charged due to gridcurrent and control grid I9 remains below ground potential for a timedepending on the time constant of capacitor 2|, resistor I3, andresistor 22. The output pulses are taken from the cathode 20 through acoupling capacitor 24-.

It should be noted that since the output voltage is taken between thecathode 20 and ground, the output capacitance will be comparatively low,and therefore the output pulse will have a rela tively steep leadingedge. It should be further noted that if the value of resistor I3 isproperly chosen with respect to the vacuum tube II and primary windingI'I resistance, the amplitude of the output pulse will be relativelygreater than, for example, the voltage across a tertiary winding ofpulse transformer I2.

It will be seen that the input voltage to this circuit is effectivelyapplied between cathode 20 and control grid I9 and the output voltage iseffectively taken between cathode 20 and ground. It will also becomeapparent to those skilled in the art, that the circuit herein set forthmight be considered a blocking oscillator connected in a boot-strapmanner.

The description hereinbefore contained has referred to the biasing ofcontrol grid I9 in accordance with the time constant of capacitor 2 I,resistor I3 and resistor 22. Thisis true in actual practice where I3 issmall compared to the value of I4. If the values are comparable, thenthe value of resistor I 4 also would have to be considered.

It will be seen that the circuit herein set forth and modifications asfall fairly within the spiri and scope thereof.

What I claim is: 1. In a pulse generating circuit, a vacuum tub having acathode, control grid and an anode, means for coupling negative triggerpulses to said anode of said vacuum tube, a pulse transformer having aprimary and a secondary winding connected on one side to said grid, aresistance connecting the other side of said secondary winding toground, a capacitor connecting said other side of said secondary windingto said cathode, means for applying trigger pulses to said secondarywinding, a load impedance connecting said cathode to ground, and meansfor coupling output pulses from said cathode load impedance.

3. A pulse generating circuit comprising a vacuum tube whose elementsinclude an anode, at least one grid, and a cathode, means forregeneratively coupling said anode and said grid so as to cause saidtube to function as a blocking oscillator, means for biasing saidoscillator normally below cutofi, load impedance means coning, saidprimary winding being connected between said anode of said vacuum tubeand a source of positive potential, capacitive means for coupling afirst terminal of said secondary winding to said cathode of said vacuumtube, means for connecting a second terminal. of said secondary windingto said control grid of said vacuum tube, said secondary winding beingcom, nected in a regenerative manner, resistive means for connectingsaid first. terminal of said secondary winding to ground, voltagedivider means for connecting said cathode of said vacuum tube to apositive potential, and, means for coupling output pulses from saidcathode of said vacuum tube.

2. A pulse generating circuit comprising a vacuum tube having at least acathode, a control grid, and an anode, means coupled to said tube forbiasing said tube normally below cut-ofi, apulse transformer having aprimary winding connected to said anode and a secondary windnectedbetween said cathode and ground potential, means for applying triggerpulses between said grid and said cathode, and means for coupling asharp, high power pulse from said impedance. when a trigger pulse.causes said oscillator to become operative. I v GEORGE P. WACHTELLIREFERENCES CITED The following references are of record in the fileofthis patent:

UNITED STATES PATENTS

